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December Weather in Iselin, United States

Last updated: June 24, 2025

In December, the average temperature in Iselin, United States hovers around 4°C (39°F), with minimums dipping as low as -11°C (13°F) and maximums reaching up to 19°C (66°F). Expect a precipitation amount of 102 mm (4.0 in) over approximately 10 days, coupled with an average humidity level of 80%. Prepare for a chilly, damp experience!

December Temperature in Iselin

In December in Iselin, the average temperature is 4°C (39°F), with maximums occasionally reaching 19°C (66°F) and minimums plunging as low as -11°C (13°F). This range makes it essential for travelers to pack layers to stay comfortable in varying conditions.

December Weather in Iselin: Daily Temperature Highs, Lows, and Averages

The chart illustrates December temperature patterns in Iselin, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Iselin, December typically has an average temperature of 4°C (39°F), with highs reaching up to 19°C (66°F) and lows dropping to around -11°C (13°F).
JanFebMarAprMayJunJulAugSepOctNovDec343743536372787670614639
Data source: Temperature data for Iselin generated using information from the Copernicus Climate Change Service.
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The average of daily temperatures (24 hours) calculated across all days in the month.

December Precipitation in Iselin

In Iselin in December, the total precipitation amount is 102 mm (4.0 in) falling over the course of 10 days.

December Precipitation Trends in Iselin

The chart displays monthly precipitation patterns in Iselin, with values for each month alongside December’s data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how December’s conditions compare to those of other months. In Iselin, December typically receives around 102 mm (4.0 inches) of precipitation spread over approximately 10 days.
JanFebMarAprMayJunJulAugSepOctNovDec66107103111118941441269113082102
Data source: Precipitation data for December generated using information from the Copernicus Climate Change Service.
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December Humidity in Iselin

In Iselin in December, humidity is 80%. With an average temperature of 4°C (39°F), this humidity feels like a damp chill that seeps into your bones, making travel uncomfortable and requiring extra layers to stay warm while navigating through the misty streets.

December Average Humidity in Iselin

This chart illustrates the average monthly humidity levels in Iselin, with December’s data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, helping you understand how conditions vary by season. In December, average humidity in Iselin is approximately 80%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec84%82%81%78%70%69%62%65%68%74%82%80%
Data source: Humidity data for December generated using information from the Copernicus Climate Change Service.

December UV Index in Iselin

In Iselin in December, the maximum UV index is 2, which corresponds to a low exposure category. With this level of UV radiation, the time to burn is approximately 45 minutes. To learn more about the hourly UV index in Iselin, you can visit Hourly UV Index in Iselin.

Maximum UV Index Levels in Iselin for December

The chart shows the monthly maximum UV Index (UVI) for Iselin in December, representing the highest UV radiation level. The UVI measures the intensity of ultraviolet radiation from the sun, indicating the potential risk of sunburn and UV-related health issues. In December, the maximum UV index in Iselin typically reaches 2, which falls under the low exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec356810101098642
Data source: Iselin December UVI data generated using information from the Copernicus Climate Change Service.

UV Risk Categories

  •  Extreme (11+): Avoid the sun, stay in shade.
  •  Very High (8-10): Limit sun exposure.
  •  High (6-7): Use SPF 30+ and protective clothing.
  •  Moderate (3-5): Midday shade recommended.
  •  Low (0-2): No protection needed.

How December Weather in Iselin Compares to Other Months

Weather in Iselin varies notably across the year, with each month offering distinct climate conditions. This page compares December’s weather to other months in Iselin, focusing on differences in temperature, rainfall, humidity, and UV levels.

This table compares monthly weather conditions in Iselin, showing how December’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather1°C (35°F)66 mm (2.6 inches)84%moderate
February Weather3°C (37°F)107 mm (4.2 inches)82%moderate
March Weather6°C (43°F)103 mm (4.0 inches)81%high
April Weather12°C (53°F)111 mm (4.4 inches)78%very high
May Weather17°C (63°F)118 mm (4.6 inches)69%very high
June Weather22°C (73°F)94 mm (3.7 inches)69%very high
July Weather26°C (79°F)144 mm (5.6 inches)62%very high
August Weather25°C (77°F)126 mm (5.0 inches)65%very high
September Weather21°C (71°F)91 mm (3.6 inches)68%very high
October Weather16°C (61°F)130 mm (5.1 inches)74%high
November Weather8°C (47°F)82 mm (3.2 inches)82%moderate
December Weather4°C (39°F)102 mm (4.0 inches)80%low

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